Gunmen have kidnapped five Polish sailors from a cargo ship off southern Nigeria, in the latest incident in a region known as a piracy hotspot, Poland’s government said Friday.

“The attack occurred at night. A group of unknown assailants boarded the boat. Five men were kidnapped” from a 16-man crew, Poland’s Foreign Minister Witold Waszczykowski told reporters in Warsaw.

“Up to now, the kidnappers have not made contact,” he said, adding that the 11 other crew members were “safe and sound” still aboard their ship, the Szafir, anchored off the Nigerian coast.

The ship’s captain along with three officers and one crew member were kidnapped, Waszczykowski said.

The other crew members locked themselves in the ship’s engine room to escape capture, Polish media reported.

The 113-metre-long vessel belonging to the Euroafrica Polish shipowner was en route to Nigeria’s Port Harcourt oil hub from Belgium.

Scores of kidnappings for ransom have occurred in the oil-rich Niger Delta, and most of the hostages have been freed after payment of a ransom.

Two Lithuanian and two Ukrainian sailors kidnapped from their ship in the same area last month were freed two weeks ago.

But Lithuanian officials refused to say how the release was secured or whether a ransom had been paid for the men’s safe return.

-Vanguard